De Morgan's rules explained

Question

Could you please explain the De Morgan\'s rules as simply as possible (e.g. to someone with only a secondary school mathematics background)?

Answer 1

Not sure why I've retained this all these years, but it has proven useful on a number of occasions. Thanks to Mr Bailey, my grade 10 math teacher. He called it deMorgan's Theorem.

!(A || B) <==> (!A && !B)
!(A && B) <==> (!A || !B)

When you move the negation in or out of the brackets, the logical operator (AND, OR) changes.